The purpose of this research project is to elucidate the mechanisms used by microorganisms to oxidize carcinogenic aromatic hydrocarbons. Particular emphasis is placed on the degradation of benzo(a)pyrene and methylcholanthrene by fungi. The latter organisms apparently use a cytochrome P-450 enzyme system and produce metabolites that are similar to those formed by mammalian liver. Such studies will provide information relative to the possible mechanisms of chemical carcinogenesis and the fate of polycyclic hydrocarbons in the environment. Specifically, the metabolites produced from benzo(a)pyrene and methylcholanthrene by intact cells and microsomal preparations of Cunninghamella elegans will be separated by high-pressure liquid chromatography and identified by conventional techniques. A bacterium Beijerinckia B8/36 has also been shown to oxidize polycyclic aromatic hydrocarbons. The metabolites produced from methylcholanthrene by this organism will be isolated and identified. Studies will also be conducted to characterize the properties of the fungal cytochrome P-450 enzyme system.